Recent developments in the use of dielectric waveguides provide functions normally associated with antenna arrays. The waveguides are generally configured as an elongated slab with a top surface, a bottom surface, a feed end, and a load end. The slab may be formed from two or more dielectric material layers such as silicon nitride, silicon dioxide, magnesium fluoride, titanium dioxide or other materials suitable for propagation at a desired frequency or wavelength of operation.
In one implementation, physical gaps are formed between the layers. A control element is also provided to adjust a size of the gaps. The control element may, for example, be a piezoelectric or electroactive material or a mechanical position control. Changing the size of the adjustable gaps has the effect of changing the effective propagation constant of the waveguide. This in turn allows for scanning the resulting beam at different angles. These devices have been designed for use at radio frequencies, acting as a directional radio antenna, and at visible wavelengths, acting as a solar energy concentrator.
See U.S. Pat. Nos. 8,582,935, 8,710,360 and 9,246,230, incorporated by reference herein, for some example implementations.
As explained in those patents, a coupling layer may also be used that has a dielectric constant that changes as a function of distance from the excitation end to the load end. By providing increased coupling between the waveguide and the correction layer in this way, horizontal and vertical mode propagation velocities may be controlled.
Adjacent dielectric layers may be formed of materials with different propagation constants. In those implementations, layers of low dielectric constant material may be alternated with layers of high dielectric constant material. These configurations can provide frequency-independent control over beam shape and beam angle.
The waveguide may also act as a feed for a line array of antenna elements. In some implementations, a pair of waveguides are used. Coupling between the variable dielectric waveguide(s) and the antenna elements can also be individually controlled to provide accurate phasing of each antenna element. See for example U.S. Pat. No. 9,509,056 incorporated by reference herein.
The elements of an antenna array may also be fed in series by a structure formed from a transmission line disposed adjacent a waveguide with reconfigurable gaps between layers. The transmission line may be a low-dispersing microstrip, stripline, slotline, coplanar waveguide, or any other quasi-TEM or TEM transmission line structure. The gaps introduced in between the dielectric layers provide certain properties, such as a variable propagation constant to control the scanning of the array.
Alternatively, a piezoelectric or ElectroActive Polymer (EAP) actuator material may provide or control the gaps between layers, allowing these layers to expand, or causing a gel, air, gas, or other material to compress. See U.S. patent application Ser. No. 14/702,147 filed May 1, 2015 incorporated by reference herein for more details.